Conventionally, electrolysis or chemical reaction is used for generating oxygen. But, these methods are unstable and inconvenient to manage. There, clean oxygen is concentrated and separated by repeating adsorbing and eliminating oxygen of 21% in the air through the PSA Process. An example of this is described in U.S. Pat. No. 5,531,807.
This device includes an air separation device in the housing for separating oxygen from the air inside the aircraft, a self-contained compressed air supply in the housing including a compressor operatively connected to the air separation device and a brushless DC motor for driving the compressor; and a circuit for connecting the D-C motor to the aircraft electrical power source including converting the A-C voltage and current on board the aircraft to D-C voltage and current for operating the motor. The device can supply oxygen with a set current value easily operated and selected by a user.
But, with the above conventional invention, it is not easy to control the concentration of oxygen. And the cited invention does not provide a solution to the polluted air.